The objectives of this research project are the continued investigation of the phospholipid-cholesterol interactions and the extension of current research to further examine the transmembrane asymmetry, flip-flop motions, and hydration of various phospholipids in bilayers. The study will utilize homogeneous, single-walled lipid vesicles in which the components are organized in bimolecular lamellae similar in form to the organization of these components in biological membranes. Principal techniques to be used are Fourier transform nuclear magnetic resonance spectroscopy, analytical ultracentrifugation, gel chromatography, UV and visible spectroscopy. Information gained from this proposal will add new dimensions to our current knowledge about lipid-lipid interactions in biological membranes. Since disturbances of lipid-lipid interactions in membranes have been strongly implicated in a variety of cardiovascular disorders, the information obtained by this proposal will be of long-range practical importance.